Facebook
header-banner-ripe_fruits_1.webp
The Future

Perfectly Ripe Fruits | How Do They Do It?

There's nothing like biting into perfectly ripe fruits, like a peach or a juicy apple. But how do these fruits make it all the way from where they’re grown, to us – and arrive at just the right time?

The science behind fruit ripening

Fruit

Ripe fruits are softer, sweeter, and more brightly coloured.

Their colour change happens as chlorophyll (the pigment that makes plants green) breaks down, while other colourful pigments like anthocyanin and carotenoids accumulate. The fruits’ sweetness comes from starches inside the fruit breaking down into simpler sugars like glucose and fructose. And their softness comes from cell walls breaking down.1

Fruits fall into two categories of ripening: either they will keep ripening by themselves once they are picked, or they won’t.

Those that continue ripening are known as climacteric and include apples, bananas, pears, apricots, peaches, blueberries and plums. Those that stop ripening once they’re picked are called non-climacteric, and include citrus fruits like lemons and limes, raspberries, strawberries, grapes, watermelon, and pineapple.2

Arriving perfectly ripe: It’s all about ethylene

Bananas

Climacteric fruits produce a burst of ethylene gas, which acts as a plant hormone, when they start ripening.  Non-climacteric fruits also produce ethylene, but they don’t release a spike of it like climacteric fruits do. They can, however, ripen further before they’re picked if they are around ethylene produced by other fruits or an external source.3

Since an ethylene spike signals the start of ripening for climacteric fruits, dampening down the levels of ethylene around them can slow down the ripening process – allowing producers to store climacteric fruits (like apples) for a long time before they reach supermarket shelves.

But how do producers keep ethylene levels down?

Delay ripening: Keep fruit cold

Warehouse

The first step for producers to keep fruit from ripening before it reaches you is to pick it at the right time. Once the concentration of ethylene reaches a tipping point of 0.1-1.0 ppm (parts per million) around the fruit, it’s too late to stop its ripening.4

Apples, for example, can be stored for several months after harvest, as long as they’re picked before they start to give off too much ethylene. But once they reach peak ripeness on the tree, they’ll only last about a month after they’re picked, depending on the storage conditions.5

One way to delay ripening is to use cold storage. Low temperatures slow down the reactions inside the fruit that make it ripen. In fact, low temperatures have been used to keep apples crisp since the 1800s, when apples were exported from the U.S. to Europe in wooden barrels in the chilly holds of old shipping vessels.6

High-tech ripening: controlling the atmosphere

Fruit for sale

Another method to delay ripening is more high-tech. Controlled-atmosphere storage (CAS) systems not only regulate the temperature of the room, but can precisely calibrate the levels of different gasses where fruits (like apples) are stored.

Fruit needs oxygen to make ethylene and ripen, so by keeping oxygen levels at 2% – instead of the 21% found in normal air – and increasing carbon dioxide levels, CAS can slow the ripening process right down and essentially put fruits into a kind of hibernation.6

A third way is to use materials that absorb ethylene from the air, like chemical compound potassium permanganate or a synthetic compound called 1-methyl-cyclo-propene (also used to keep cut flowers fresh), to limit the fruit’s exposure to ethylene.1 

Once a producer is ready to ship the apples to supermarkets and greengrocers, both ethylene and acetylene – similar chemical compounds – can be used to ripen them, in ripening rooms with controlled temperature and humidity, to make sure they’re crisp and juicy when they reach consumers.7

How to ripen fruit at home

Fruit bowl

While a lot of technology keeps the fruits in good condition before they reach you, you can take advantage of the same chemistry to help them cross the threshold from almost-ripe to perfect in your fruit bowl at home.

Bananas produce a lot of ethylene, so you can give other fruit, like not-quite-ripe peaches, a helping hand by storing them together. The ethylene from the banana should help ripen the peaches quicker than if they were left to their own devices.

Keep updated with the latest news about your food with our newsletter.

Subscribe

Related articles

Most viewed

The Future

How Plants Are Grown In Space | Space Food Technology

Keeren Flora

To travel into deep space, such as a mission to Mars, astronauts must be able to grow their food.…

The Future

Aquaponics | Sustainable Urban Farming

Samanta Oon

When you think of aquaponics, you might imagine a cutting-edge, modern farm. This can be true, but…

Earth First

5 Reasons to Use Edible Utensils

Jane Alice Liu

You ordered take-out, and the restaurant forgot to give you plastic utensils. Maybe that wasn't so…

Earth First

Building a Future with Crops From the Past

Benedetta Gori

Beyond the familiar fields of wheat, rice, and maize lies a forgotten realm of diverse crops that…

The Future

Food on Ships | Secrets to Preserving Food

Annabel Slater

Food preservation is a battle against bacteria, a fight against fungi. On ship journeys, how have…

The Future

Cleaning The Seas with Mussel and Oyster Farms

Aran Shaunak

Some mussel and oyster farms work in a way that produces food, minimises environmental damage, and…

The Future

Perfectly Ripe Fruits | How Do They Do It?

Kelly Oakes

There's nothing like biting into perfectly ripe fruits, like a peach or a juicy apple. But how do…

The Future

The Fight to End Harmful Fisheries Subsidies

Maria Pinto

Overfishing is one of the most critical global challenges facing our oceans, posing significant…

The Future

Precision Fermentation: Past, Present, and Future Promise

Anne Reshetnyak

Microorganisms and fermentation have been crucial for food safety and flavour for thousands of…

The Future

Is Organic Food Really Better?

Silvia Lazzaris

We’re going organic. But it’s no silver bullet.

The Future

Food made with human bacteria exists

Luke Cridland, Meghan Horvath

We may associate bacteria with disease and infections, but there’s actually quite a lot of…

Earth First

Is Climate Change Making Our Food Less Nutritious?

Lauren Lewis

Recent studies suggest that climate change could be reducing the nutrient content of certain crops.…

Keep updated with the latest news about your food with our newsletter

Subscribe

Follow Us